U.S. patent application number 11/966314 was filed with the patent office on 2009-07-02 for solid-state optical modulator.
This patent application is currently assigned to Texas Instruments Incorporated. Invention is credited to Simon Joshua Jacobs.
Application Number | 20090168136 11/966314 |
Document ID | / |
Family ID | 40797902 |
Filed Date | 2009-07-02 |
United States Patent
Application |
20090168136 |
Kind Code |
A1 |
Jacobs; Simon Joshua |
July 2, 2009 |
SOLID-STATE OPTICAL MODULATOR
Abstract
A spatial light modulator comprises a solid-state chiral
material disposed between electrodes such that the polarization
direction of the polarized light incident thereto can be controlled
through an electrical field established between the electrodes.
Inventors: |
Jacobs; Simon Joshua;
(Lucas, TX) |
Correspondence
Address: |
TEXAS INSTRUMENTS INCORPORATED
P O BOX 655474, M/S 3999
DALLAS
TX
75265
US
|
Assignee: |
Texas Instruments
Incorporated
Dallas
TX
|
Family ID: |
40797902 |
Appl. No.: |
11/966314 |
Filed: |
December 28, 2007 |
Current U.S.
Class: |
359/246 ;
257/E21.002; 438/29 |
Current CPC
Class: |
G02F 1/13718 20130101;
G02F 1/0136 20130101; G02F 2201/343 20130101; G02F 1/03
20130101 |
Class at
Publication: |
359/246 ; 438/29;
257/E21.002 |
International
Class: |
G02F 1/01 20060101
G02F001/01; H01L 21/02 20060101 H01L021/02 |
Claims
1. A spatial light modulator for use in a display system,
comprising: an array of light modulating devices, each comprising:
a solid-state chiral material that is disposed between first and
second electrodes such that an electrical field can be established
across the solid-state chiral material.
2. The spatial light modulator of claim 1, wherein the first
electrode is transmissive to the visible light; and wherein the
second electrode is reflective to the visible light.
3. The spatial light modulator of claim 2, wherein the first
electrode comprises an indium-titanate-oxide layer.
4. The spatial light modulator of claim 1, wherein the solid-state
chiral material comprises an inorganic material or an organic
material.
5. The spatial light modulator of claim 4, wherein the solid-state
chiral material comprises an electrically conductive or
electrically insulating material.
6. The spatial light modulator of claim 1, wherein the solid-state
chiral material is a left-handed or a right-handed chiral
material.
7. The spatial light modulator of claim 1, wherein the solid-state
chiral material exhibits a polarization direction that is
determined by the electrical field.
8. The spatial light modulator of claim 1, wherein the solid-state
chiral material has a primary optical axis.
9. The spatial light modulator of claim 1, wherein the first or the
second electrode of said light modulating device is connected to an
electrode of another light modulating device such that said first
or the second electrode and the electrode of said another light
modulating device form a substantially continuous electrode
layer.
10. A method of displaying an image, comprising: providing a
spatial light modulator that comprises an array of individually
addressable pixels, wherein each pixel comprises: a solid-state
chiral material that is disposed between first and second
electrodes such that an electrical field can be established across
the solid-state chiral material; directing a beam of polarized
light to the pixels of the spatial light modulator; modulating the
pixels of the spatial light modulator based on the image to be
displayed by adjusting the electrical fields applied to the
solid-state chiral materials of the pixels; passing the light from
the pixels of the spatial light modulator through a polarizer; and
directing the light after the polarizer onto a display target.
11. The method of claim 10, wherein the polarized light is incident
to the solid-state chiral materials such that the incident
polarized light is substantially not-parallel to a primary axis of
the solid-state chiral material of the pixels.
12. The method of claim 10, wherein the step of directing the beam
of polarized light to the pixels of the spatial light modulator
further comprises: directing the beam of polarized light to the
pixels of the spatial light modulator through another polarizer,
wherein said another polarizer has a polarization direction is
substantially perpendicular to a polarization direction of said
polarizer that is disposed after the spatial light modulator.
13. A display system, comprising: a light source providing a light;
a spatial light modulator comprising an array of pixels, each pixel
comprising: a solid-state chiral material that is disposed between
first and second electrodes such that an electrical field can be
established across the solid-state chiral material; a first
polarizer having a first polarization direction; and a second
polarizer having a second polarization direction that is
substantially perpendicular to the first polarization direction;
and a set of optical elements for directing the light toward the
spatial light modulator and for directing the light from the
spatial light modulator onto a display target.
14. The system of claim 13, further comprising: a half-waver plate
disposed between the light source and the spatial light
modulator.
15. The system of claim 14, wherein the first polarizer is disposed
between the half-wave plate and the spatial light modulator; and
the second polarizer is disposed between the spatial light
modulator and the display target.
16. The system of claim 14, wherein the first electrode is
transmissive to the visible light; and wherein the second electrode
is reflective to the visible light.
17. The system of claim 16, wherein the first electrode comprises
an indium-titanate-oxide layer; and wherein the solid-state chiral
material comprises an inorganic material or an organic
material.
18. A method of making a spatial light modulator, comprising:
providing a semiconductor substrate having formed thereon a first
array of electrodes and circuits; forming a layer of solid-state
chiral material on the provided semiconductor substrate; and
forming a second array of electrodes on the formed solid-state
chiral material.
19. The method of claim 18, wherein the second array of electrodes
are transmissive to visible light.
20. The method of claim 19, wherein the electrodes of the second
array of electrodes each comprising a plurality of layers that
comprises an electrically conductive and transparent layer.
21. The method of claim 18, wherein the semiconductor substrate is
a portion of a semiconductor wafer that comprises a plurality of
die areas.
22. A method of forming a spatial light modulator, comprising:
providing a semiconductor substrate having formed thereon a first
array of electrodes that are electrically conductive; providing a
light transmissive substrate having formed thereon a second array
of electrodes that are transparent and electrically conductive;
forming a solid-state chiral material on the semiconductor
substrate or the light transmissive substrate; and assembling the
light transmissive substrate and the semiconductor substrate.
23. The method of claim 22, wherein the step of assembling the
light transmissive substrate and the semiconductor substrate
further comprises: assembling the light transmissive substrate and
the semiconductor substrate such that at least one of the
electrodes in the first electrode array is associated with at least
one of the electrode of the second electrode array.
24. The method of claim 22, wherein the step of assembling the
light transmissive substrate and the semiconductor substrate
further comprises: assembling the light transmissive substrate and
the semiconductor substrate such that substantially no air gap is
present between the solid-state material and the first electrode
array or the second electrode array.
25. The method of claim 22, wherein the solid-state chiral material
has a primary optical axis.
Description
TECHNICAL FIELD OF THE DISCLOSURE
[0001] The technical field of this disclosure relates to the art of
optical modulators, and more particularly to the art of solid-state
electro-optic modulators.
BACKGROUND OF THE DISCLOSURE
[0002] Optical modulators are optical devices in which
signal-controlled elements are used to modulate incident light.
Microelectromechanical system (MEMS) based spatial light modulators
and electro-optical modulators are two types commonly used optical
modulators. A typical MEMS based spatial light modulator comprises
an array of mechanically deflectable elements, such as deflectable
mirror plates of micromirror devices (e.g. DLP.RTM. by Texas
Instruments, Inc.) or movable membranes (e.g. IMOD by QualComm,
Inc.). Electro-optic modulators are optical modulators whose signal
controlled elements exhibit electro-optic effects, based on the
effect of which modulations are performed. A typical
electro-optical modulator employs nematic materials, which are
commonly known as liquid-crystal materials, such as
Liquid-crystal-on-silicon (LCoS). A common feature of these nematic
materials in existing electro-optical modulators is that the mass
centers of nematic molecules have no long range order, and these
molecules tend to be parallel to common axes.
[0003] Because operations of current MEMS based spatial light
modulators are based upon the mechanical movements of deflectable
elements (e.g. the mirror plates of micromirror devices); and the
mechanical movements often take longer time (e.g. 20 ms or longer)
to respond to control signals, performance of the MEMS based
spatial light modulators is limited by the slow response time of
the mechanical elements. Moreover, mechanical elements often occupy
spaces that are much larger than the smallest size of a typical
semiconductor circuit (e.g. an addressing electrode and electrical
circuit used for deflecting the movable element) achievable by
current integrated circuit fabrication technologies. Incorporation
of mechanical elements certainly encumbers achieving small size
MEMS based spatial light modulators.
[0004] Current electro-optical spatial light modulators also have
larger response time, which significantly limits their
applications. For spatial light modulators based on nematic
materials, the response time of the spatial light modulator is
determined by the response time of nematic molecules of the spatial
light modulator, which is typically in the order of microseconds.
The response time of the spatial light modulator can be even larger
due to re-orientations of nematic molecules during state
transitions. Moreover, the delicate property due to the intrinsic
liquid-crystal natural of the nematic based spatial light modulator
limits the application of existing nematic based spatial light
modulators.
[0005] Therefore, it is always desired for spatial light modulators
that are preferably robust, reliable, fast, high resolution, and
lower power-consumptive.
SUMMARY
[0006] In one example, a spatial light modulator for use in a
display system is provided herein. The spatial light modulator
comprises: an array of light modulating devices, each comprising: a
solid-state chiral material that is disposed between first and
second electrodes such that an electrical field can be established
across the solid-state chiral material.
[0007] In another example, a method of displaying an image is
provided herein. The method comprises: providing a spatial light
modulator that comprises an array of individually addressable
pixels, wherein each pixel comprises: a solid-state chiral material
that is disposed between first and second electrodes such that an
electrical field can be established across the solid-state chiral
material; directing a beam of polarized light to the pixels of the
spatial light modulator; modulating the pixels of the spatial light
modulator based on the image to be displayed by adjusting the
electrical fields applied to the solid-state chiral materials of
the pixels; passing the light from the pixels of the spatial light
modulator through a polarizer; and directing the light after the
polarizer onto a display target.
[0008] In yet another example, a display system is provided. The
system comprises: a light source providing a light; a spatial light
modulator comprising an array of pixels, each pixel comprising: a
solid-state chiral material that is disposed between first and
second electrodes such that an electrical field can be established
across the solid-state chiral material; a first polarizer having a
first polarization direction; and a second polarizer having a
second polarization direction that is substantially perpendicular
to the first polarization direction; and a set of optical elements
for directing the light toward the spatial light modulator and for
directing the light from the spatial light modulator onto a display
target.
[0009] In yet another example, a method of making a spatial light
modulator is provided. The method comprises: providing a
semiconductor substrate having formed thereon a first array of
electrodes and circuits; forming a layer of solid-state chiral
material on the provided semiconductor substrate; and forming a
second array of electrodes on the formed solid-state chiral
material.
[0010] In still yet another example, a method of forming a spatial
light modulator is provided. The method comprises: providing a
semiconductor substrate having formed thereon a first array of
electrodes that are electrically conductive; providing a light
transmissive substrate having formed thereon a second array of
electrodes that are transparent and electrically conductive;
forming a solid-state chiral material on the semiconductor
substrate or the light transmissive substrate; and assembling the
light transmissive substrate and the semiconductor substrate.
[0011] In yet another example, a method of making a spatial light
modulator is provided. The method comprises: providing a frame that
comprises a light transmissive substrate and a semiconductor
substrate that is spaced apart from the light transmissive
substrate so as to form a gap therebetween, wherein the light
transmissive substrate and the semiconductor substrate each
comprise an array of electrodes; and inserting a solid-state chiral
material into the gap between the light transmissive substrate and
the semiconductor substrate.
[0012] In another example, a wafer is disclosed herein. The wafer
comprises: a set of die areas, each die area comprises first and
second array of electrodes disposed therebetween a chiral material
that is in the solid-state.
[0013] In still yet another example, a method of making a spatial
light modulator is disclosed. the method comprises: providing a
semiconductor wafer that comprises a set of die areas, in each of
which a first array of electrodes and circuits are formed; forming
a layer of solid-state chiral material on the semiconductor wafer
in each die area; forming a second array of electrodes on the
solid-state chiral material; and singulating the dies from the
semiconductor wafer.
[0014] In yet another example, a method of making a spatial light
modulator is disclosed. The method comprises: providing a
transparent wafer that comprises a first set of die areas; forming
an array of transparent electrodes in each one of the die areas of
the first set of die areas in the transparent wafer; forming a
layer of solid-state chiral material on the transparent substrate;
and assembling the first set of dies to a second set of dies on a
semiconductor wafer having formed thereon an array of
non-transparent electrodes and circuits in each die area of the
second set of die areas; and singulating the assemblies so as to
obtain individual spatial light modulators.
BRIEF DESCRIPTION OF DRAWINGS
[0015] FIG. 1 schematically illustrates a cross-sectional view of a
solid-state electro-optical modulator;
[0016] FIG. 2 schematically illustrates the variation of the
polarization direction of the modulated light from the solid-state
electro-optical modulator in FIG. 1;
[0017] FIG. 3a schematically illustrates a top view of an exemplary
spatial light modulator comprising an array of solid-state
electro-optical modulators in FIG. 1;
[0018] FIG. 3b schematically illustrates a top view of another
exemplary spatial light modulator comprising an array of
solid-state electro-optical modulators in FIG. 1;
[0019] FIG. 4a through FIG. 4d schematically illustrate an
exemplary method of making an spatial light modulator having an
array of solid-state electro-optical modulators in FIG. 1;
[0020] FIG. 5a illustrates a cross-sectional view of a portion of
an exemplary electrode array for use in a spatial light modulator
having an array of solid-state electro-optical modulators in FIG.
1;
[0021] FIG. 5b illustrates a cross-sectional view of a portion of
another exemplary array of electrodes for use in a spatial light
modulator having an array of solid-state electro-optical modulators
in FIG. 1;
[0022] FIG. 6 illustrates a cross-sectional view of a portion of an
exemplary transparent electrode for use in the solid-state
electro-optical modulator in FIG. 1;
[0023] FIG. 7 schematically illustrates an exemplary electrical
connection scheme for use in a spatial light modulator having an
array of solid-state electro-optical modulators in FIG. 1;
[0024] FIG. 8 schematically illustrates a perspective view of an
exemplary package that comprises a spatial light modulator having
an array of solid-state electro-optical modulators in FIG. 1;
[0025] FIG. 9 schematically illustrates a method of making a
spatial light modulator on wafer level, wherein each spatial light
modulator comprises an array of solid-state electro-optical
modulators in FIG. 1;
[0026] FIG. 10a through FIG. 10d schematically illustrate another
exemplary method of making a spatial light modulator having an
array of solid-state electro-optical modulators in FIG. 1;
[0027] FIG. 11a and FIG. 11b schematically illustrate another
exemplary wafer-level fabrication method for making a spatial light
modulator having an array of solid-state electro-optical modulators
in FIG. 1;
[0028] FIG. 12a and FIG. 12b schematically illustrate yet another
exemplary method of making a spatial light modulator having an
array of solid-state electro-optical modulators in FIG. 1;
[0029] FIG. 13a and FIG. 13b schematically illustrate yet another
exemplary method of making a spatial light modulator having an
array of solid-state electro-optical modulators in FIG. 1; and
[0030] FIG. 14 schematically illustrates an exemplary display
system employing a spatial light modulator having an array of
solid-state electro-optical modulators in FIG. 1;
DETAILED DESCRIPTION OF SELECTED EXAMPLES
[0031] Disclosed herein is a solid-state electro-optic modulator
that comprises a solid-state chiral material disposed between first
and second electrodes such that the polarization direction of the
polarized light (electromagnetic wave) incident thereto can be
modulated through an electrical field established between the first
and second electrodes.
[0032] A "chiral material" is material that comprises chiral
objects of substantially the same handedness. A chiral object (e.g.
molecules and molecule combinations with helical chiral
microstructures) is a three-dimensional body whose property renders
it non-congruent with its mirror image by translation or rotation.
The term "handedness", as known by those skilled in the art, refers
to whether a chiral object is "right-handed" or "left-handed." If a
chiral object is left-handed (right-handed), its mirror image is
right-handed (left handed). In this regard, the mirror image of a
chiral object is its enantiomorph with opposite handedness. The
chiral objects can be randomly or regularly orientated (resulting
in a dominant orientation or a principal optical axis); and
uniformly or non-uniformly distributed within the space of the
modulator.
[0033] A solid-state chiral material is a chiral material that
comprises chiral objects whose mass centers have a long range order
as compared to that of nematic liquid-crystal materials. For
example, the mass centers of the chiral objects in a solid-state
chiral material can be arranged into a 2-dimensional or
3-dimensional lattice with certain lattice parameters. It is noted
that even though the chiral objects are arranged such that the mass
centers of the chiral objects exhibit a long range order, the
chiral objects may be arranged randomly or regularly. The chiral
material may or may not exhibit a principal optical axis. Moreover,
a bulk body composed of a chiral material may also have defects
and/or vacancies and/or even other non-chiral objects though it is
less preferred.
[0034] In the following, the solid-state electro-optic modulator
will be discussed with selected examples. It will be appreciated by
those skilled in the art that the following discussion is for
demonstration purpose, and should not be interpreted as a
limitation. Many variations within the scope of the disclosure are
also applicable. In the following, "light" is referred to
electro-magnetic waves with exceedingly wide range of wavelengths,
depending upon specific applications. For example, the "light" or
the illumination can be visible light when the solid-state
electro-optical modulator is used in an image display system. The
light can alternatively be infrared or ultraviolet light or light
with other wavelengths. For given light with a specific wavelength
or a specific wavelength range, the chiral material of the
solid-state electro-optical modulator is capable of modulating the
given light by rotating the polarization direction of the given
light.
[0035] Referring to the drawings, FIG. 1 schematically illustrates
a cross-sectional view of an exemplary solid-state electro-optic
modulator (hereafter SSEO modulator). The SSEO modulator (100)
comprises solid-state chiral material 104 disposed between
electrodes 102 and 106 that are provided for establishing
electrical field E across the solid-state chiral material (104).
Electrode 102 is electrically conductive and transparent to the
incident light such that the illumination light to be modulated can
pass through electrode 102 and are incident to chiral material 104.
For example, electrode 102 is preferably capable of passing 85% or
more, 90% or more, 95% or more of the incident illumination light.
The transparent electrode (102) may have other features, such as an
anti-reflection layer for improving the transmission of the
incident light.
[0036] Electrode 106 is electrically conductive, and preferably has
a surface that is reflective to the illumination light to be
modulated, such as a surface capable of reflecting 50% or more, 70%
or more, 85% or more, and 95% or more of the illumination light to
be modulated. The reflective surface of electrode 106 can be a
surface of a single material that is reflective to the incident
light, or alternatively, a reflective layer coated on a
non-reflective material. In another example, the surface of
electrode 106 may comprise a light absorbing layer for absorbing
light incident thereto. For example, the light absorbing layer can
be a layer that is capable of absorbing 50% or more, 70% or more,
85% or more, and 95% or more of the light incident thereto.
[0037] The solid-state chiral material (104) is preferably, though
not required, an inorganic material with molecules of helical
chiral microstructures, such as MgF.sub.2 and many other suitable
materials. For example, the chiral material can be any suitable
inorganic solid-state materials, and more preferably (though not
required), an inorganic solid-state material that is compatible
with (e.g. can be fabricated by) standard thin film processing and
with a high dielectric breakdown strength. A dielectric breakdown
strength is referred to as the maximum electric field strength that
the dielectric material can withstand intrinsically without
breaking down, i.e., without experiencing failure of its dielectric
(or insulating) properties. Other exemplary chiral materials can be
metal or semiconductor oxides, such as SiO.sub.2 and
Al.sub.2O.sub.3. Mass centers of the molecules of the solid-state
chiral material exhibit a long range order as compared to the
molecules in the liquid-crystal state. In other words, chiral
material 104 exhibits macro properties of solid-state materials,
such as specific melting points. Because the solid-state chiral
material (104) is in solid-state and exhibits properties of
solid-state materials, it can be more thermally and mechanically
stable than many other nematic materials including liquid-crystal
materials. This property can be of great importance in designing,
fabricating, assembling, delivering, installing, and maintaining
SSEO modulators using the solid-state chiral materials. Application
of such SSEO modulators may not require additional containers as
compared to nematic materials (e.g. liquid-crystal materials) in
current spatial light modulators.
[0038] Molecules of chiral material 108 have substantially the same
handedness--right-handedness or left-handedness, depending upon the
specific material. The molecules can be regularly arranged within
the space between electrodes 102 and 106 such that a dominant or
principal optical axis can be defined. As schematically illustrated
in FIG. 1, in the plane of the principal axis and the normal
direction of solid-state chiral material 104, the principal axis
has a principal angle .OMEGA. with the normal direction.
Alternatively, the molecules can be randomly disposed between
electrodes 102 and 106 such that there are no principal optical
axes or dominant optical axes.
[0039] Within the space between electrodes 102 and 106, molecules
of the chiral material can be uniformly distributed such, even
though defects and/or vacancies may exit within the space.
Alternatively, molecules of the chiral material can non-uniformly
fill in the space between electrodes 104 and 106. For example,
molecules of the chiral material (104) can fill in the space
between electrodes 102 and 106 in forms of molecular clusters with
each molecular cluster comprising a group of molecules. In this
instance, mass centers of the molecules may or may not maintain a
long range order; but the mass centers of the molecular clusters
exhibit a long range order. The molecules in each cluster may or
may not be regularly oriented and/or distributed, that is, optical
axes of the individual molecules in the cluster may or may not
define a dominant or principal optical axis; and the mass centers
of the individual molecules in each cluster may or may not
regularly arranged. Even though not required, it is preferred that
there is substantially no air gap between the solid-state chiral
material (104) and the electrodes (102 and 106). The solid-sate
chiral material (104), however, can be connected to each one of the
electrodes (102 and 106) through other suitable layers or elements.
For example, an optical index matching layer, which is transmissive
to the illumination light, can be disposed between the lower
surface of the transmissive electrode (102) and the top surface of
solid-state chiral material 104 so as to matching the refractive
indices of the transmissive electrode 102 and solid-state chiral
material 104. To avoid unwanted displacement of the solid-state
chiral material (104) inside the space between electrodes 102 and
106, a bonding layer (or layers) can be applied to secure the
attachment of chiral material (104) to electrode 106 and/or to
transmissive electrode 102.
[0040] The solid-state chiral material (104) exhibits an
electro-optical property. Specifically, a beam of polarized
incident light changes its polarization direction depending upon
the electrical field E applied across the solid-state chiral
material (104) as the polarized light travels inside the
solid-state chiral material (104). As schematically illustrated in
FIG. 1, polarized incident light passing through electrode 102 is
incident to chiral material 104 with an incident angle
.theta..sub.in between the incident light and the normal direction
of the solid-state chiral material (104). The polarized light
propagates within the solid-state chiral material (104); and is
reflected by the reflective surface of electrode 106. The reflected
polarized light from electrode 106 propagates within the
solid-state chiral material (104) towards transmissive electrode
102; and exits from transmissive electrode 102. During the
propagation within the solid-state chiral material towards
electrode 106 and towards transmissive electrode 102, the polarized
light changes its polarization direction depending upon the
electrical field E (e.g. the amplitude of electrical field E). As a
consequence, the light exiting from the solid-state chiral material
(hereafter modulated light) may have a different polarization
direction than the incident light. The reflection angle
.theta..sub.out between the modulated light and the normal
direction of the solid-state chiral material (104) can be the same
as the incident angle .theta..sub.in.
[0041] For demonstration purpose, FIG. 2 schematically illustrates
the variation of the polarization direction of the modulated light
over the applied electrical field E. Referring to FIG. 2, when the
chiral material is a left-handed chiral material, the polarization
plane of the modulated light is rotated left-handedly in relation
to the polarization plane of the incident light before modulation
when the electrical field E is substantially zero, as shown in the
left panel of FIG. 2. When electrical field is non-zero, the
polarization plane of the modulated light is rotated right-handedly
relative to the incident light before modulation, as shown in the
right panel of FIG. 2. Similarly, when the chiral material is a
right-handed material, the polarization plane of the modulated
light is rotated right-handedly relative to the incident light
before modulation in the absence of the electrical field; and the
polarization plane of the modulated light is rotated left-handedly
relative to the incident light before modulation in the presence of
a non-zero electrical field.
[0042] The amount of the rotated angle of the polarization plane
may follow the Kerr effect, wherein the resulted refraction index
difference is proportional to the electrical field squared.
Alternatively, the amount of the rotated angle of the polarization
plane may follow the Pockel effect, wherein the resulted refraction
index difference is proportional to the electrical field
quadrupled.
[0043] In modulation operations, incident light is incident onto
the modulator at an incident angle .theta..sub.in. The incident
light angle can be of any values, though it is preferred not equal
to the principal angle .OMEGA. that is defined as the angle between
the principal axis of the solid-state chiral material (104) and the
normal direction of the solid-state chiral material (104).
[0044] Because the modulation of the SSEO modulator (100) as
described above with reference to FIG. 1 is accomplished through
the electro-optical property of the solid-state chiral material
(104), the response time of the solid-state electro-optical
modulator is substantially determined by the electro-optical
response time of the solid-state chiral material (104) to the
applied driving signal (e.g. the electrical field E), which can be
in the order of nanoseconds. This response speed, which is
proportional to the reciprocal of the response time, can be 1000
times faster than the response speed of typical existing
liquid-crystal based or micromirror based optical modulators.
Accordingly, the SSEO modulator as discussed above can be operated
at a speed in the order of GHZ; and the time period for switching
the SSEO modulator from one state (e.g. the OFF-state) to a
different state (e.g. the ON-state) and stabilizing at the
different state can be 500 nanoseconds or less, 200 nanoseconds or
less, 100 nanoseconds or less, 50 nanoseconds or less, 20
nanoseconds or less, and 10 nanoseconds or less.
[0045] Due to the absence of mechanically movable elements and the
fact that the physical size of the SSEO modulator can be determined
solely on the size(s) of the electrodes or the electrical
circuit(s) connected to the electrodes, the SSEO modulator can be
much smaller than typical existing MEMS-based spatial light
modulators. With the current integrated circuit fabrication
techniques, electrodes and electrical circuits (e.g. memory cells)
can be made with sizes of sub-microns. Accordingly, a SSEO
modulator can have a size in the order of sub-microns. Small size
SSEP modulators can be of great importance in display systems.
Specifically, small size SSEO modulators enable a spatial light
modulator to be used in an image display system to have a native
resolution (the total number of optical modulators, which are
referred to as pixels of the spatial light modulator) of
640.times.480 (VGA) or higher, such as 800.times.600 (SVGA) or
higher, 1024.times.768 (XGA) or higher, 1280.times.1024 (SXGA) or
higher, 1280.times.720 or higher, 1400.times.1050 or higher,
1600.times.1200 (UXGA) or higher, 1920.times.1080 or higher,
1.times.10.sup.6 or higher, 1.times.10.sup.7 or higher,
1.times.10.sup.8 or higher, 1.times.10.sup.9 or higher, or integer
multiples and fractions of these resolutions. Of course, other
resolutions are also applicable.
[0046] Because the physical shape of a SSEO modulator can be
determined solely on the physical shape of the electrodes (e.g.
electrode 102 and 106) of the SSEO modulator, the SSEO modulator
can be formed into any desired shapes, such as circular,
rectangular, square, trapezoidal, hexagonal, and many other shapes.
When multiple SSEO modulators are to be used together, such as an
array of SSEO modulators in a spatial light modulator of a display
system or in a optical switch in optical signal communications, the
chiral materials of individual SSEO modulators in the array can be
connected together so as to form a substantially continuous
solid-state chiral material layer. Of course, the solid-state
chiral materials of the individual SSEO modulators can be connected
in any desired shapes, such as strips, frames, blocks, and
segments. As a way of example, FIG. 3a schematically illustrates a
spatial light modulator comprising an array of SSEO modulators as
discussed above with reference to FIG. 1.
[0047] In the example as shown in FIG. 3a, the SSEO modulators
(e.g. SSEO modulator 110) of SSEO modulator array 108 in a spatial
light modulator are illustrates as dashed circles. Each SSEO
modulator is an individually addressable pixel of the spatial light
modulator. Operational states of the pixels (SSEO modulators) are
controlled by the individual electrical fields applied to the
solid-state chiral materials. In order to individually control the
SSEO modulators, each SSEO modulator can have a separate
transmissive electrode (i.e. electrode 102 in FIG. 1); and the
reflective electrodes (i.e. electrode 106 in FIG. 1) of the SSEO
modulators may or may not be connected together. In another
example, the transmissive electrodes of the SSEO modulators can be
connected together; while the reflective electrodes of the SSEO
modulators are separate. Regardless of different configurations of
the electrodes, solid-state chiral materials of the SSEO modulators
may or may not be form a continuous layer.
[0048] Another exemplary spatial light modulator having an array of
SSEO modulators as discussed above with reference to FIG. 1 is
schematically illustrated in FIG. 3b.
[0049] Referring to FIG. 3b, the spatial light modulator comprises
an array (112) of SSEO modulators (e.g. SSEO modulator 114) as
discussed above with reference to FIG. 1. In this particular
example, each SSEO modulator takes a shape of hexagon; and the SSEO
modulators of the array form a hexagonally compact lattice in the
spatial light modulator. With this hexagonal compact arrangement,
the spatial light modulator can achieve higher fill factor than
other configurations.
[0050] It is noted that the spatial light modulators in FIG. 3a and
FIG. 3b are two of many possible examples. A spatial light
modulator comprising SSEO modulators may have many other possible
configurations. For example, a spatial light modulator may have any
desired number of SSEO modulators. The SSEO modulators in a spatial
light modulator may have any suitable shapes and/or spatial
arrangements. In particular, a spatial light modulator and/or the
array of SSEO modulators in the spatial light modulator may have a
rectangular shape with an aspect ratio of 16:9, 4:3, 16:10, or
other desired aspect ratios.
[0051] The SSEO modulators and the array of SSEO modulators in a
spatial light modulator as discussed above can be fabricated in
many ways, one of which is schematically illustrated in FIG. 4a
through FIG. 4d. Referring to FIG. 4a, semiconductor substrate 116,
such as a silicon substrate, is provided. Electrode array 118
comprising an array of non-transparent electrodes 118, such as
electrode 106, can be formed on substrate 116. Electrical circuits,
such as memories, can also be formed on or in the semiconductor
substrate (116) for controlling the electrical states of the
electrodes in electrode array 118. Exemplary electrical circuits
are schematically illustrated in FIG. 5a and FIG. 5b.
[0052] Referring to FIG. 5a, a row of an exemplary electrical
circuit array 126 is schematically illustrated therein. In this
example, each one of the non-transparent electrodes (e.g. electrode
106) of the row is connected to a memory cell (e.g. memory cell
134) of a row in an array of memory cells. Each memory cell
comprises a transistor, such as an NMOS or PMOS transistor, and a
capacitor for storing a digital bit that corresponds to a high
voltage or a low voltage. The voltage node of each memory cell,
such as the node connecting the drain of the transistor and one of
the metallic plates of the capacitor, is connected to a
non-transparent electrode (e.g. electrode 106). Contents of the
memory cells are written and accessed through wordlines (e.g.
wordline 130) and bitlines, wherein the wordlines are connected to
the gates of the transistors of the memory cells; and the bitlines
are connected to the sources of the transistors of the memory
cells. The wordlines can be connected to a wordline driver (128)
that provides wordline signals for activating the memory cells. The
bitlines can be connected to a bitline driver (132) for reading
contents stored in the activated memory cells. In the example as
shown in FIG. 5a, the memory cells in each row of the memory cell
array are connected to one wordline. In another example, the memory
cells in each row of the memory cell array can be connected to
multiple wordlines such that different wordlines are connected to
different memory cells. Other wordline connecting schemes are also
applicable, which will not be detailed herein.
[0053] In the example shown in FIG. 5a, each memory cell has a
capacitor that has a grounded metallic plate. In another example,
the grounded metallic plates of the capacitors can be instead
connected to a pumping line 136, as shown in FIG. 5b. The pumping
line is capable of providing pumping signals whose voltage may vary
over time and can be controlled so as to improve the performance of
the memory cells.
[0054] It is noted that FIG. 5a and FIG. 5b illustrate only two of
many possible examples. Other electrical configurations are also
applicable. For example, instead of reflective electrodes (e.g.
electrode 106), the memory cells in FIG. 5a or FIG. 5b can be
connected to the transmissive electrodes, such as electrode 102 in
FIG. 1, of the SSEO modulators.
[0055] Referring again to FIG. 4a, the electrical circuits can be
formed using a standard integrated circuit fabrication method on
the semiconductor substrate (116). The array of non-transparent
electrodes (118) can be formed by depositing a layer of selected
conductive material on the semiconductor substrate followed by
lithographic patterning. The conductive layer is preferably
non-transparent and reflective to the illumination light to be
modulated. When a transparent or less reflective material is used,
a reflective layer (not shown in the figure) can be formed on the
formed non-transparent electrodes. Other optical layers, such as a
light absorbing layer capable of absorbing 80% or more, 90% or more
of the illumination light to be modulated, can be formed on the
semiconductor substrate for reducing unwanted light scattering.
When the solid-state chiral material is to be used, an electrically
insulating layer can be further deposited on top of the electrodes.
It is noted that each non-transparent electrode can be formed into
any desired shapes, such as rectangular, square, trapezoid, circle,
and many other desired shapes.
[0056] A solid-state chiral material (104) can be formed on the
semiconductor substrate having formed thereon the non-transparent
electrode array 118, as shown in FIG. 4b. Referring to FIG. 4b, the
solid-state chiral material (104) can be formed using a
glancing-angle-deposition method (GLAD) while rotating the
semiconductor substrate (116) so as to construct the helical
microstructure in molecules. After deposition, a patterning process
may be performed so as to define individual pixels regions in the
spatial light modulator. The patterning process may not be
performed if the solid-state chiral material (104) is desired to be
a substantially continuous layer across a group of SSEP modulators
or all SSEP modulators in the spatial light modulator. An array of
transparent (or semi-transparent) electrodes 120, such as
transparent electrode 104, is formed on the solid-state chiral
material (104), as shown in FIG. 4c.
[0057] Referring to FIG. 4c, the transparent (or semi-transparent)
electrode array 120 can be formed by depositing an electrode layer
on the formed solid-state chiral material (104). The electrode
layer comprises a material that is electrically conductive and
transparent or semi-transparent to the illumination light that is
to be used. The deposited electrode layer is patterned using a
standard lithography technique such that each transparent electrode
(e.g. electrode 102) is at a location corresponding to a location
of at least one of the non-transparent electrodes (e.g. electrode
106) on the semiconductor substrate (116) so as to form paired
electrodes (e.g. electrodes 102 and 106) with the solid-state
chiral material being laminated therebetween.
[0058] The transparent electrode can be formed from any suitable
electrical conductive materials. For example, the electrically
conductive layer may comprise metalloid, metal alloys that comprise
two or more elemental metals, intermetallic compounds, ceramics,
organics, and/or polymers. An intermetallic compound may be
composed of transition metals, including but not limited to early
and late transition metals.
[0059] A ceramic is a compound wherein a metal (or metalloid) is
bonded to a non-metal. The ceramic for the transmissive and
electrically conductive layer can be an oxide, a nitride or a
carbide of a metal or a metalloid, preferably a metal oxide or a
metalloid oxide binary or ternary compound. Alternatively, the
transparent electrode can be a multilayered structure comprising at
least an electrical conductive and transparent layer. Other layers,
such as mechanical enhancing layers, optical layers for enhancing
transmission of the illumination light and/or for polarizing
non-polarized illumination light, stiction layers for improving
stiction of the transparent electrodes to the surface of the
solid-state chiral material, or any combinations thereof, can be
formed on either one of the top and bottom surfaces of the
transparent electrode.
[0060] As a way of example, the transparent and electrically
conductive layer may comprise: indium-titanate-oxide, TiO.sub.x,
doped ZnO.sub.x (such as ZnO.sub.x doped with aluminum, gallium,
fluorine, boron, and indium), SnO.sub.2, doped SnO.sub.2 (such as
SnO.sub.2 doped with fluorine and antimony), GdIn.sub.xO.sub.y,
doped InO.sub.x (such InO.sub.x doped with fluorine, tin and other
suitable conductive organics and polymers, such as Baytron.RTM.
conductive polymers (e.g. Baytron.RTM.)). Other transparent and
conductive materials may also be used, such as CdSn.sub.xO.sub.y
(e.g. Cd.sub.2SnO.sub.4, CdSnO.sub.3 and CdIn.sub.2O.sub.4),
An.sub.2SnO.sub.4, MgIn.sub.2O.sub.4, Y doped CdSb.sub.2O.sub.3,
ZnSnO.sub.3, GaINO.sub.3, Zn.sub.2In.sub.2O.sub.5, and
In.sub.4Sn.sub.3O.sub.12, indium doped CdO, CuAlO.sub.2,
Cu.sub.2SrO.sub.2, and CuGaO.sub.2 doped Ga.sub.2O.sub.3,
Ti.sub.2O.sub.3, PbO.sub.2, and Sb.sub.2O.sub.5.
[0061] When the solid-state chiral material is electrically
conductive, a transparent and electrically insulating layer may be
provided for avoiding electrical short between the solid-state
chiral material and the transparent electrodes. Such electrically
insulating and transparent layer can be separate from the
transparent electrode, or can be a member of the multilayered
transparent electrode.
[0062] The electrically insulating materials can be materials of
high optical indices or materials of low optical indices. For
example, the transparent and electrically insulating material with
high optical indices can be TiO.sub.x and Nb.sub.2O.sub.5,
HfO.sub.2, Ta.sub.2O.sub.5, ZrO.sub.2, Si.sub.3N.sub.4,
La.sub.2O.sub.3, and Nd.sub.2O.sub.3. The transparent and
electrically insulating materials with low optical indices can be
CaF.sub.2, SiO.sub.2, MgF.sub.2, and Al.sub.2O.sub.3. Of course,
the materials listed above are for demonstration purposes, and are
not intend to include all possible transparent and electrically
conductive (or insulating) materials that are applicable in the
SSEO modulators.
[0063] In selecting and applying the transparent and electrically
conductive and insulating materials for the transparent electrodes
(e.g. electrode 102 in FIG. 4c), the electrically conductive
(and/or insulating) layers can themselves be single or multilayered
structures to improve the anti-reflection properties of the layers.
Alternatively, the electrically conductive and insulating layers
can be alternatively stacked on the light transmissive substrate.
For example, a material of high optical index can be stacked closer
to the light transmissive substrate than those materials of low
optical indices so as to form an optical index gradient from the
surface of the transparent electrode to the air, which in turn
improves the anti-reflection of the incident light.
[0064] As a way of example, a laminated transparent electrode is
schematically illustrated in FIG. 6. Referring to FIG. 6, the
laminate transparent electrode (102) comprises niobium oxide layer
(or TiO.sub.x layer) 138, silicon oxide layer 140,
indium-titanium-oxide layer 142, and another silicon oxide layer
144. The niobium oxide layer (or TiO.sub.x layer) 138 can be
provided for improving the attachment of the transparent electrode
(102) to the solid-state chiral material (104 in FIG. 4c). The
first silicon oxide layer 140 is provided for electrically
insulating the ITO layer (142) and the niobium oxide layer (or
TiO.sub.x layer) 138. The ITO layer (142) is provided for carrying
electrical voltages for maintaining desired electrical fields
across the solid-state chiral material (e.g. 104 in FIG. 4c). The
second silicon oxide layer 144 can be provided for protecting the
ITO layer (142). Both of the first and second oxide layers 140 and
144 can also be used as mechanical enhancing layer for enhancing
the mechanical stability of the transparent electrode (102).
[0065] The layers of the multilayered transparent electrode (102)
can be formed using any suitable film fabrication methods, such as
chemical-vapor-deposition (CVD), physical-vapor-deposition (PVD),
and physical-electro-chemical-vapor phase deposition (PECVD). As an
example, the niobium oxide layer (138) may have a thickness of from
10 angstroms to 5000 angstroms, preferably from 50 angstroms to 200
angstroms, and more preferably around 100 angstroms. The optical
index of this niobium oxide layer (138) is preferably from 1 to
2.7, more preferably from 1.5 to 2.5, and more preferably around
2.3. The first silicon oxide layer (140) may have a thickness of
from 10 angstroms to 5000 angstroms, preferably from 50 angstroms
to 500 angstroms, and more preferably around 400 angstroms. The
optical index of this silicon oxide layer (140) is preferably from
1 to 1.7, more preferably from 1.2 to 1.5, and more preferably
around 1.46. The indium-titanium-oxide layer (142) may have a
thickness of from 10 angstroms to 5000 angstroms, preferably from
50 angstroms to 1000 angstroms, and more preferably around 600
angstroms. The optical index of this ITO layer (142) is preferably
from 1 to 2.7, more preferably from 1.2 to 1.9, and more preferably
around 1.8. The second silicon oxide layer (144) may have a
thickness of from 10 angstroms to 5000 angstroms, preferably from
50 angstroms to 1500 angstroms, and more preferably around 900
angstroms. The optical index of this silicon oxide layer (144) is
preferably from 1 to 1.7, more preferably from 1.2 to 1.5, and more
preferably around 1.46.
[0066] Referring again to FIG. 4c, after forming the transparent
electrode array 120 on solid-state chiral material 104, fabrication
of the spatial light modulator (156) having a solid-state chiral
material can be finished.
[0067] As an alternative feature, a protective substrate (122) can
be formed on the transparent electrode array 120 for protecting the
transparent electrode array 120, as well as other device
components, as shown in FIG. 4d. The protection substrate (122) is
transparent to the illumination light to be modulated; and
preferably (though not required) has an optical index that matches
the optical index of the transparent electrodes. The protection
substrate (122) may have other suitable features, such as optical
films formed thereon for improving the optical performance of the
substrate (122), and/or mechanical.
[0068] It can be desired to extend electrical connections of the
transparent electrodes to the lower semiconductor substrate, on
which electrical contacting pads can be formed. The electrical
contacting pads are often provided for connecting the SSEP
modulators of the spatial light modulator to external electrical
power(s) and data/control signals. Such electrical connection
extension can be accomplished in many ways, one of which is through
a shim (124) as schematically illustrated in FIG. 4d. The
connection of the shim (124) to the electrodes is better
illustrated in FIG. 7.
[0069] Referring to FIG. 7, semiconductor substrate 116 has formed
thereon an array of non-transparent electrodes 118. A set of
electrical contacting pads 152 is deployed around an edge of the
semiconductor substrate (116); and is preferably outside the
electrode array 118. Shim contacts 148a and 148b each being
electrically conductive are formed on the semiconductor substrate
and are connected to one of the contacting pads (e.g. contacting
pad 152).
[0070] The transparent electrode array (120), which is disposed
such that the solid-state chiral material (not shown) is laminated
between the transparent electrode array (120) and the
non-transparent electrode array (118), is electrically connected to
shim contacts 146a and 146b. Shim contacts 146a, 146b, 148a, and
148b are formed at locations such that shim contact 146a is aligned
to and electrically connected to shim contact 148a; and shim
contact 146b is aligned to and electrically connected to shim
contact 148b. With such configuration, electrical connections to
the transparent electrodes of the transparent electrode array (120)
can be extended to the contacting pads (e.g. pad 152) on the
semiconductor substrate (116).
[0071] The fabricated spatial light modulator (e.g. 156 in FIG. 4c
or FIG. 4d) can be disposed in a package for protection as
schematically illustrated in FIG. 8. Referring to FIG. 8, spatial
light modulator 156 having an array of SSEO modulators as discussed
above with reference to FIG. 4c or FIG. 4d is disposed on a
supporting surface of a cavity in package substrate 158. A package
cover can be attached to the surface of the package substrate (158)
so as to seal the spatial light modulator (156) inside the cavity.
The packaged spatial light modulator (154) can then be used in a
display system. In other examples, especially when the spatial
light modulator (156) comprises a protection substrate (e.g.
protection substrate 122 as illustrated in FIG. 4d), the spatial
light modulator (156) may not be packaged for protection.
[0072] The above discussed spatial light modulator can be
fabricated on the wafer level as demonstrated in FIG. 9.
Specifically, a plurality of dies (e.g. die 162) can be formed in
semiconductor wafer 160. A spatial light modulator can be formed on
each one of the dies of the wafer (160) using a fabrication method
as discussed above with reference to FIG. 4a through FIG. 4c or
FIG. 4d. The spatial light modulators can be formed on the dies at
the same time. After the fabrication, the dies are separated from
the wafer so as to obtain individual spatial light modulators, such
as spatial light modulator 156 in FIG. 4c or FIG. 4d.
[0073] During the wafer level fabrication, a packaging process can
be performed so as to obtain packaged spatial light modulators,
such as packaged spatial light modulator 154 as illustrated in FIG.
8. For example, before or after fabrications of individual dies but
before singulation, a planar package substrate can be attached to
the bottom surface (the surface opposite to the top surface wherein
the non-electrodes are formed) of the semiconductor wafer. Other
suitable materials, such as compliant die attach materials for
improving thermal dissipation, for improving the mechanical
stability, and/or for other desired purposes. Depending upon
whether a package cover is expected for each spatial light
modulator in the package, a spacer can be provided so as to
maintain a constant distance between the package cover and the
package substrate. Attachment of the spacer can be performed after
the singulation.
[0074] Alternatively, individual package substrates, such as a
package substrate with concaves, can be disposed at each location
of the spatial light modulator and attached to the bottom surface
of the semiconductor wafer.
[0075] Instead of continuously fabricating the components of the
spatial light modulator on the semiconductor substrate as discussed
above with reference to FIG. 4a through FIG. 4c, components of the
spatial light modulator can be formed separately followed by
assembly, as schematically illustrated in FIG. 10a through FIG.
10d.
[0076] Referring to FIG. 10a, substrate 112 that is transparent to
the illumination light to be modulated, such as glass, quartz, and
sapphire, is provided. Electrode array 120 having an array of
transparent electrodes, such as electrode 102, is fabricated on
substrate 122. Other desired layers, such as optical layers,
mechanical enhancing layers, and/or stiction enhancing layers can
also be formed as discussed above with reference to FIG. 4c.
Solid-state chiral material 104 is then formed on the fabricated
transparent electrode array 120 as shown in FIG. 10b. The
solid-state chiral material (104) can be formed using the same
method as discussed above with reference to FIG. 4b.
[0077] A semiconductor substrate (116) is provided as illustrated
in FIG. 10c. The semiconductor substrate comprises electrode array
118 that comprises an array of non-transparent electrodes (e.g.
electrode 106) and electrical circuits (not shown), as discussed
above with reference to FIG. 4a.
[0078] The transparent substrate (122) having formed thereon the
transparent electrode array (122) can then be assembled to
semiconductor substrate 116, as shown in FIG. 10d. Referring to
FIG. 10d, semiconductor substrate 116 is assembled to substrate 122
such that solid-state chiral material (104) is laminated between
electrode arrays 118 and 120.
[0079] After the assembling, the non-transparent electrodes of
electrode array 118 can be associated with the transparent
electrodes of electrode array 120 so as to enabling establishments
of electrical fields across the solid-state chiral material(s).
Shim 124 can be proved for extending electrical connections to the
transparent electrodes to the electrical contacting pads on the
semiconductor substrate, as discussed above with reference to FIG.
7, which will not be repeated herein. The fabricated spatial light
modulator can, though not necessarily, be placed in a package for
protection as discussed above with reference to FIG. 8.
[0080] Alternative to forming the solid-state chiral material (104)
on the transparent substrate (122) as discussed above with
reference to FIG. 10b, the solid-state chiral material (104) can be
formed on the semiconductor substrate (116) after forming the
electrode array 118 and the electrical circuits on the
semiconductor substrate (116). The semiconductor substrate (116)
with the solid-state chiral material can then be assembled to the
transparent substrate 122 having formed thereon electrode array
120.
[0081] The fabrication method as discussed above with reference to
FIG. 10a through FIG. 10d can be performed on the wafer level, as
schematically demonstrated in FIG. 11a and FIG. 11b.
[0082] Referring to FIG. 11a, wafer 164 is a transparent wafer
composed of the same material as transparent substrate 122 in FIG.
10a. The transparent wafer (164) comprises multiple die areas, such
as die area 166. The fabrication steps as discussed above with
reference to FIG. 10a and FIG. 10b can be performed in each die
area on the wafer (164).
[0083] Wafer 144 is a semiconductor wafer composed of the same
material as the semiconductor substrate 116 in FIG. 10c. The
semiconductor wafer comprises multiple die areas, such as die area
170. The fabrication steps as discussed above with reference to
FIG. 10c can be performed in each die area on the semiconductor
wafer (168).
[0084] Semiconductor wafer 168 and the transparent wafer (164) can
then be assembled. After assembling, the dies in the two wafers are
individually assembled as discussed above with reference to FIG.
10d. The assembled dies are then separated so as to obtain
individual spatial light modulators. It is noted that the wafers
may or may not have the same number of dies, and as such, some of
the dies in one wafer may not be successfully assembled to dies on
the other wafer.
[0085] During the wafer-level fabrication, a packaging process can
be performed so as to obtain packaged spatial light modulators as
shown in FIG. 8. For example, before or after fabrications of
individual dies but before singulation, a planar package substrate
can be attached to the bottom surface (the surface opposite to the
top surface wherein the non-electrodes are formed) of the
semiconductor wafer. Other suitable materials, such as compliant
die attach materials for improving thermal dissipation, for
improving the mechanical stability, and/or for other desired
purposes. Depending upon whether a package cover is expected for
each spatial light modulator in the package, a spacer can be
provided so as to maintain a constant distance between the package
cover and the package substrate.
[0086] Attachment of the spacer can be performed after the
singulation. Alternatively, individual package substrates, such as
a package substrate with concaves, can be disposed at each location
of the spatial light modulator and attached to the bottom surface
of the semiconductor wafer.
[0087] The SSEO modulators and the array of such modulators can
alternatively be fabricated by forming a frame comprising the
desired electrodes followed by inserting a selected solid-state
chiral material into the frame, as schematically illustrated in
FIG. 12a through FIG. 13b.
[0088] Referring to FIG. 12a, frame 164 is provided. The frame
(164) comprises semiconductor substrate 116, transparent substrate
122, and spacer 124, which can be the shim as discussed above. The
semiconductor substrate (116) comprises electrode array 118 that
comprises an array of non-transparent electrodes, such as electrode
106. The semiconductor substrate can be prepared in a way as
discussed above with reference to FIG. 4a through FIG. 4d or FIG.
10a through FIG. 10d.
[0089] The transparent substrate (122) and the array (120) of
transparent electrodes (e.g. electrode 102) formed thereon can be
prepared in a way as discussed above with reference to FIG. 4a
through FIG. 4d or FIG. 10a through FIG. 10d. The prepared
transparent substrate (122) and semiconductor substrate 116 can be
bonded together using spacer 124 so as to form frame 164 such that
each reflective electrode (e.g. electrode 106) of the electrode
array 118 on the semiconductor substrate (116) is aligned to a
transparent electrode (e.g. electrode 102) on the transparent
substrate (122). The transparent substrate (122) and the
semiconductor substrate (116) form an empty space therebetween.
Solid-state chiral material 104, which is prepared separately, can
be slide into the space of the frame (164), as illustrated in FIG.
12b.
[0090] When the transparent electrodes (e.g. electrode 102 in FIG.
1) of the SSEO modulators are a continuous electrode layer, such
continuous electrode layer can be used to form a frame with the
semiconductor substrate and the spacer, as illustrated in FIG.
13a.
[0091] Referring to FIG. 13a, transparent electrode layer 168 is
spaced apart from semiconductor substrate (116) by the spacer 124
so as to form frame 166 with a gap between the transparent
electrode layer (168) and the semiconductor substrate (116). The
prepared solid-state chiral material (104) can then be inserted
into the gap to form the spatial light modulator (167), as shown in
FIG. 13b.
[0092] The SSEO modulator as discussed above has many applications,
one of which is spatial light modulators in display systems. As a
way of example, an exemplary display system employing a spatial
light modulator having an array of SSEO modulators as discussed
above is schematically illustrated in FIG. 14.
[0093] Referring to FIG. 14, display system 170 comprises light
source 172, polarize 176, spatial light modulator 156, polarization
analyzer 178, and display target 180. As an alternative feature,
half-waver plate 174 can be provided.
[0094] Light source 172 is designed for providing polarized
illumination light for the display system; which can be composed of
any suitable light emitting devices, such as arc lamps and
solid-state light emitting devices (e.g. lasers and
light-emitting-diodes (LEDs). When solid-state light emitting
devices are used, the light source may comprise an array of
solid-state light emitting devices capable of emitting different
colors, such as colors selected from red, green, blue, and white.
Because a single solid-state light emitting device generally has a
narrow characteristic bandwidth that may not be optimal for use in
display systems employing spatial light modulators, multiple
solid-state light emitting devices can be used for providing light
of each color so as to achieve optimal bandwidth for specific
display systems. For example, multiple lasers or LEDs with slightly
different characteristic spectra, such as 20 nm or less wavelength
separation, can be used to produce a color light such that the
characteristic spectra of the multiple lasers or LEDs together form
an optimal spectrum profile of the display system. Exemplary laser
sources are vertical cavity surface emitting lasers (VCSEL) and
Novalux.TM. extended cavity surface emitting lasers (NECSEL), or
any other suitable laser emitting devices.
[0095] Polarizer 176 is provided for passing the illumination light
(or the portion of the illumination light) with a pre-defined
polarization direction. The polarizer (176) has a polarization
direction that is preferably perpendicular to that of the
polarization analyzer 178.
[0096] The spatial light modulator (156) comprises an array of SSEO
modulators as discussed above for modulating the polarized
illumination light incident thereto into modulated light with a
polarization direction different from that of the light incident to
the spatial light modulator (156).
[0097] The modulated light is directed to polarization analyzer 178
that has a polarization direction perpendicular to that of the
polarizer 176. With the above configuration, the modulated light
from a SSEO modulator of the spatial light modulator (156) can be
stopped by the polarization analyzer (178) when the electrical
field applied to the SSEO modulator is substantially zero. The
stopped modulated light from the SSEO modulator results in a dark
pixel on the display target. The modulated light from a SSEO
modulator in the spatial light modulator with a non-zero electrical
field can pass through the polarization analyzer (178) and arrived
at the display target (180)--resulting in a bright pixel on the
display target (180). The combination of the dark and bright pixels
on the display target forms the desired image on the display
target. Gray-scaled imaged can be formed using a pulse-width
modulation technique; and color imaged can be formed using a
combination of a pulse-width-modulation technique and a
sequential-field-illumination technique or other suitable
techniques.
[0098] As the alternative feature, half-waver plate 174 can be
provided for pre-polarizing the illumination light from the light
source. For improving the optical efficiency, such as the
brightness of the image produced on the display target, other
optical elements can be provided. For example, a polarization
converter can be provided before polarizer 176 for converting
substantially all component of the illumination light from the
light source into one component with the polarization direction
defined by the polarizer (176). As such substantially all
illumination light can pass through the polarizer (176).
[0099] The display target can be a screen on a wall or the like, or
can be a member of a rear projection system, such as a rear
projection television. The display system can be any suitable
display system, such as a front projector, a rear projection
television, or a display unit for use in other systems, such as
mobile telephones, personal data assistants (PDAs), hand-held or
portable computers, camcorders, video game consoles, and other
image displaying devices, such as electronic billboards and
aesthetic structures.
[0100] It will be appreciated by those of skill in the art that a
new and useful solid-state electro-optical modulator and a spatial
light modulator having an array of solid-state electro-optical
modulators have been described herein. In view of the many possible
embodiments, however, it should be recognized that the embodiments
described herein with respect to the drawing figures are meant to
be illustrative only and should not be taken as limiting the scope
of what is claimed. Those of skill in the art will recognize that
the illustrated embodiments can be modified in arrangement and
detail. Therefore, the devices and methods as described herein
contemplate all such embodiments as may come within the scope of
the following claims and equivalents thereof.
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